Finally, just what rom-com fans have been craving: a bisexual Balkan version of Mamma Mia! Set on a sun-soaked tourist island off Croatia's Adriatic coast, this lighthearted midsummer sex comedy marks a sharp change of direction for Bosnian writer-director Jasmila Zbanic, whose two previous features were both bleak, award-winning dramas about the lingering scars of war. Co-written by the Bosnian-American Aleksandar Hemon, Love Island is a brightly colored cocktail of romantic cliches, broad humor and bombastic Bollywood-style musical numbers. But it is also a lively, escapist fantasy with an infectious lust for life.

A Swiss-German-Bosnian-Croatian co-production featuring dialogue in multiple European languages, the comedy in Love Island often gets lost in translation. But the universal rom-com trappings and majority English dialogue should help the film's prospects in overseas markets. Judging by its rapturous reception at the Sarajevo Film Festival this week, Zbanic's feel-good fairy tale will have strong commercial appeal locally.

Bosnian screen icon Ermin Bravo, whose past credits include all of Zbanic's films to date plus Angelina Jolie's Balkan war drama In The Land of Blood and Honey, plays Grebo, a boorish but essentially likeable former rock singer from Sarajevo. On vacation in Croatia with his heavily pregnant French wife, Liliane (Greek-born Attenberg veteran Ariane Labed), Grebo is gearing up for a sedate future of marriage and fatherhood. But then both husband and wife begin picking up heavy erotic vibes from a sexy Romanian resort employee, Flora (Ada Condeescu).

Sneaking away from Liliane, Grebo makes a shameless bid to seduce Flora after winning her over with his party piece, a comically heartfelt karaoke version of the uber-kitsch power ballad Wind of Change by German rockers Scorpions — which becomes an increasingly surreal musical motif throughout the film. Liliane responds by confronting her husband with shock revelations about her past lesbian relationships and soft-porn movies. Deception becomes infidelity, and the marriage hits the rocks.

Love Island is not a subtle movie. The dialogue, written and spoken by people for whom English is plainly a second or third language, is full of corny lines and clunky twists. The camera work also feels oddly jittery, with lots of sudden crash zooms that would make more sense in a mockumentary than in this kind of sweet comic trifle. The characters are cartoons, their romantic crisis deeply implausible and their final reconciliation risibly silly.

And yet, when it finally settles down, Zbanic's outwardly conventional plot becomes a warmhearted, quietly subversive celebration of pan-sexual freedom and guilt-free pleasure. As fleeting and frothy as a holiday romance, Love Island is a bumpy ride at times. But any movie that features punk-haired bisexual mermaids dancing underwater to German industrial techno-rockers Rammstein is clearly not following the mainstream rule book.